PoC server, PoC terminal, floor control method, and PoC terminal control method

ABSTRACT

A floor can be fairly acquired in a PoC communication. In the PoC server which controls a floor in a PoC communication, a floor is put in an idle state in a PoC communication after a session establishing process required in the PoC communication. The information about the floor idle state is notified to terminals TA and TC which perform the PoC communication. When the PoC communication is initiated, the idle state of the floor is simultaneously noticed to both calling and called users, thereby realizing fair acquisition of a floor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a PoC server, a PoC terminal, a floorcontrol method, and a PoC terminal control method, and more specificallyto a PoC server, a PoC terminal, a floor control method, and a PoCterminal control method for realizing a PoC communication in a mobileobject communication network.

2. Description of the Related Art

Realization of PoC (Push-to-Talk over Cellular) communication isscheduled which makes it possible to use a mobile terminal device, suchas a cellular phone, like a transceiver and realize communication amongmultiple users in a group only by touching a button.

PoC communication is quick communication means to be used between twousers or in a group, and it is possible to use a terminal device like atransceiver in the PoC communication. The operation for startingconversation is performed not by pressing dial buttons but by simplypressing a particular button.

Currently, PoC communication is standardized(OMA-RD_PoC-V1_(—)0-20041115-C) based on the PoC Charter(OMA-CHARTER_PoC-V1_(—)0-20031014-A) by the OMA (Open Mobile Alliance),an industry organization which promotes standardization of mobileapplication techniques.

In order to perform PoC communication, it is the premise that acommunication channel has been already formed. Following a Registrationmessage and an INVITE message by SIP (Session Initiation Protocol),acquisition of the floor (right to speak) by RTP (Real Time Protocol) isperformed.

Description will be made on processings from starting PoC communicationwhen a communication channel has not been formed yet to ending the PoCcommunication, with reference to FIGS. 9 to 14. In the figures, thereare shown three terminals TA, TB and TC which are provided with a PoCcommunication function and a PoC server 100 which controls a PoCcommunication service.

(Formation of a Communication Channel)

In order to perform PoC communication, it is necessary that acommunication channel have been formed as a premise. To form acommunication channel, communication channel establishment requestsignals 50A, 50B and 50C are sent by the respective terminals to the PoCserver 100. Thereby, receiving the communication channel establishmentrequest signals 50A, 50B and 50C, the PoC server 100 formscommunications channels 51A, 51B and 51C between the respectiveterminals and itself, as shown in FIG. 10. These communication channels51A, 51B and 51C are communication channels enabling packetcommunication, such as a GPRS (General Packet Radio Service) network anda WLAN (Wireless Local Area Network). The PoC server performs positionregistration processing and the like for the terminals against asubscriber information management server (Home Location Register Server)200.

(Registration Processing and Invitation Processing)

After the communication channels 51A, 51B and 51C are formed by theabove processing, Registration processing is performed. In this example,the Registration processing is performed by the terminal TA of a user A,and a PoC conversation group consisted of the three users A, B and C isspecified. In the Registration processing, REGISTER messages 52A, 52Band 52C are sent by the terminal TA of the user A, the terminal TB ofthe user B and the terminal TC of the user C, respectively. When 200 OKsignals 54A, 54B and 54C are sent after response signals 53A, 53B and53C from the PoC server to the sent REGISTER message are received,respectively, the Registration processing is completed.

After the Registration processing, the process proceeds to Invitationprocessing. In the Invitation processing, an INVITE message 55A is sentfrom the terminal TA of the user A to the terminal TB of the user B andthe terminal TC of the user C in the same PoC conversation group, asshown in FIG. 11. This INVITE message includes destination information(information for identifying the terminal TB of the user B and theterminal TC of the user C), transmission source information (informationfor identifying the terminal TA of the user A), a call identifier (suchas a Call-ID), a header portion configured by a transmission route andthe like, and a body portion configured by detailed information aboutthe medium (classification whether voice or picture, band and the like).

If the terminals TB and TC of the user B and the user C are set to anautomatic mode when they receive the INVITE messages 55B and 55C sentvia the PoC server 100, then 200 OK signals 56B and 56C areautomatically sent, and PoC communication is enabled. On the other hand,if the terminals TB and TC are set to a manual mode, then a 180 ringingsignal is automatically sent first (not shown). Furthermore, byperforming an operation such as pressing a button, the 200 OK signals56B and 56C are outputted, and thereby, PoC communication is enabled.

When, while only the terminal TA of the user A and the terminal TB ofthe user B are performing PoC communication with each other, anoperation such as pressing a button is performed on the terminal TC ofthe user C in the same PoC conversation group, a 200 OK signal isoutputted, and PoC communication by the three users A, B and C isenabled. That is, any member in the same PoC conversation group can joinPoC communication later by performing an operation such as pressing abutton.

In order to disconnect PoC communication, a BYE message is sent from aterminal to the PoC server. Thereby, the terminal leaves the PoCconversation group which it has joined.

The above processing is performed in accordance with SIP (SessionInitiation Protocol) provided in the specification RFC3261 by the IETF(Internet Engineering Task Force).

(Acquisition of the Floor)

In PoC communication, a user cannot speak without acquiring the floor.That is, a user can be a speaker only when he has the floor. He is alistener when he does not have the floor.

In order to acquire the floor when PoC communication is being performed,it is necessary to send and receive signals in accordance with RTP(Real-time Transport Protocol) and send a Floor Request signal. Here, asshown in FIG. 12, a floor request signal 57A is sent from the terminalTA of the user A. If the PoC server which has received the floor requestsignal 57A permits the floor, it returns a Floor Grant signal 58A to theterminal TA of the user A. The floor grant signal 58A includesidentification information about the terminal to which the floor ispermitted, information indicating the time of permission, and the like.

On the other hand, if the PoC server which has received the floorrequest signal 57A does not permit the floor, it returns a Floor Denysignal 59A, as shown in FIG. 13. This floor deny signal 59A includesidentification information about the terminal to which the floor is notpermitted, identification information about the terminal which currentlyhas the floor, information about the time of permission, and the like.

By making a speech while pressing a button, in the terminal which hasthe floor, the voice is sent to other terminals in the same PoCconversation group as packet data, and it is possible to speak in thegroup. The floor is held while the button is pressed. If the fingerleaves the button and stops pressing it, the floor is lost. In thiscase, when pressing the button is stopped, a Floor Release signal 60A issent from the terminal to the PoC server as shown in FIG. 14, and astate is caused in which no terminal has the floor (Floor Idle).

In addition to releasing the floor by releasing a button from thecondition of being pressed as described above, the floor may be releasedby time-out of a timer.

The protocol for performing the PoC communication described above has ahierarchical structure. That is, as shown in FIG. 15, the protocol has astructure in which RTP is located above a communication channel, and SIPis located above RTP.

SUMMARY OF THE INVENTION

(Floor when PoC Communication is Initiated)

In the above-mentioned PoC communication system according to the OMAspecification, when the called terminal (terminal TB or terminal TC inthe case above) returns a response, the terminal which has transmitted aconnection request (terminal TA in the case above) is controlled toacquire a floor. It is explained below by referring to FIG. 16. In FIG.16, the operations of the terminal TA, the terminal TC, and the PoCserver 100 performed when the PoC communication is initiated are shown.

When a predetermined button is operated in the terminal TA to initiatethe PoC communication (S101), a SIP session establishing process isperformed between the terminal TA and the PoC server 100 (S102). Also,the SIP session establishing process is performed between the PoC server100 and the terminal TC (S103).

Then, the PoC server 100 transmits a floor grant signal indicating thepermission of a floor to the terminal TA (S104). Thus, the user of theterminal TA can recognize the permission of a floor (S105). On the otherhand, the PoC server 100 transmits a floor taken signal indicating theidentification information about the user who has acquired a floor tothe terminal TC (S106). Thus, the user of the terminal TC can recognizethat the user of the terminal TA is the speaker (S107). Then, when theuser of the terminal TA speaks, a media streaming signal is transmittedto the terminal TC through the PoC server 100, thereby transmitting andreceiving audio and video data (S108, S109). The floor grant signal andthe floor taken signal are transmitted and received by a packet(hereinafter referred to as an APP packet) of an RTCP (RTP controlprotocol) for defining a specific function of an application. A mediastreaming signal is transmitted and received by a packet of the RTP.

In the above-mentioned processes, a terminal which has transmitted aconnection request acquires a floor on a priority basis. In this method,there can be a case where the acquisition of a floor is unfairlypermitted, and there can be the problem that although a user of aterminal first acquiring a floor (terminal TA in the case above) speaksnothing, other users cannot acquire a floor without waiting until afloor is released to them.

(Releasing a Floor)

In the PoC communication system according to the above-mentioned OMAspecification, a procedure of notifying that a floor is released when aterminal acquires a floor, and a floor is released after a predeterminedtime is prescribed. That is, as shown in FIG. 17, it is assumed that afloor grant signal is transmitted from the PoC server 100 to theterminal TA which has acquired a floor (S200). Then, the PoC server 100transmits a floor revoke signal to the terminal TA which has acquired afloor to notify the terminal that a floor is going to be released(S201). Then, the terminal TA immediately transmits a floor releasesignal to the PoC server 100 (S202). Upon receipt of the signal, the PoCserver 100 transmits to the terminal TA a floor idle signal indicatingthat a floor is released (S203).

However, since a user who has acquired a floor does not know theremaining time (that is, a time period up to the expiration time) of thefloor, there can be the case where a floor is released during speech,thereby causing an inconvenience.

The present invention has been developed to solve the above-mentionedproblems, and an object of the present invention is to provide a PoCserver, a PoC terminal, a floor control method, and a PoC terminalcontrol method capable of realizing fair acquisition of a floor.

Another object of the present invention is to provide a PoC server, aPoC terminal, a floor control method, a PoC terminal control methodcapable of allowing a user to know the remaining time of his or herfloor.

The PoC server according to claim 1 of the present invention controls afloor in a PoC communication, and includes: setting means for setting afloor idle state in the PoC communication after a session establishingprocess necessary for the PoC communication; and floor idle-notificationmeans for notifying a terminal which performs the PoC communication thatthe floor is released. When the PoC communication is initiated, a flooridle state is simultaneously notified to both calling and called users,thereby realizing fair acquisition of a floor.

The PoC server according to claim 2 of the present invention controls afloor in a PoC communication, and includes advance-release-notificationmeans for notifying a PoC terminal which has acquired a floor for apredetermined time of at least one of an advance-release-notice, aremaining time of the floor, and time up to a warning operation for anadvance-release-notice before releasing the floor. By notifying a PoCterminal which has acquired a floor of an advance-release-notice of afloor and remaining time of the floor, the convenience of a user can beenhanced.

In the PoC server according to claim 3 based on claim 2, when theadvance-release-notification means gives a notice of time up to awarning operation for an advance-release-notice, the means notifies ofthe remaining time up to termination of a floor and an alert marginindicating time from the warning operation to the termination of thefloor when a floor permission notification is issued. By notifying of analert margin indicating time from a warning operation to the terminationof a floor together with the remaining time up to the termination of thefloor, the time from a warning to the termination of the floor can beleveled independent of a model specification on the PoC terminal side.

The PoC terminal according to claim 4 of the present invention includes:reception means for receiving an advance-release-notification of a floortransmitted from a PoC server which controls a floor in a PoCcommunication; and warning means for performing a predetermined warningoperation when the reception means receives theadvance-release-notification. When a user receives anadvance-release-notification, the notification is made by voice, displayon a display unit, vibration, etc., thereby enhancing the convenience ofa user.

The floor control method according to claim 5 of the present inventioncontrols a floor in a PoC communication, and includes: a step of settinga floor idle state in the PoC communication after a session establishingprocess necessary for the PoC communication; and a step of notifying aPoC terminal which performs the PoC communication that the floor isidle. By simultaneously notifying both users of calling and calledterminals of a floor idle state when a PoC communication is initiated,fair acquisition of a floor can be realized.

The floor control method according to claim 6 of the present inventioncontrols a floor in a PoC communication, and includes a step ofnotifying a PoC terminal which has been provided with a floor of atleast one of an advance-release-notice, a remaining time of the floor,and time taken up to an issue of a warning for an advance-release-noticebefore releasing the floor. By notifying the PoC terminal which hasacquired a floor of an advance-release-notice of the floor and theremaining time, the convenience of the user can be enhanced.

The PoC terminal control method according to claim 7 of the presentinvention includes: a receiving step of receiving anadvance-release-notification of a floor transmitted from a PoC serverwhich controls a floor in a PoC communication; and a warning step ofperforming a predetermined warning operation when theadvance-release-notification is received in the receiving step. When anadvance-release-notification is received, the notification is made byvoice, display on a display unit, vibration, etc., thereby enhancing theconvenience of a user.

As described above, the present invention has the effect of realizingfair acquisition of a floor by simultaneously notifying both users ofcalling and called terminals of a floor idle state when a PoCcommunication is initiated.

Furthermore, by notifying the PoC terminal which has acquired a floor ofan advance-release-notice of the floor and the remaining time, a warningthat the floor is released is given, thereby enhancing the convenienceof the user.

Furthermore, by notifying of an alert margin indicating the time from awarning operation to the termination of a floor together with theremaining time up to the termination of the floor when a floorpermission notification is issued, the time from a warning to thetermination of the floor can be leveled independent of a modelspecification on the PoC terminal side, thereby realizing a leveled PoCservice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sequence chart showing the operation performed when a PoCcommunication is initiated according to a mode for embodying the presentinvention;

FIG. 2 is a block diagram showing an example of the configuration of aPoC terminal according to a mode for embodying the present invention;

FIG. 3 is a block diagram showing an example of the configuration of aPoC server according to a mode for embodying the present invention;

FIGS. 4A and 4B show an example of the structure of an APP packet;

FIG. 5 is a sequence chart showing an example of the operationsperformed when an advance-release-notice of a floor is issued;

FIG. 6 is a sequence chart showing another example of the operationsperformed when an advance-release-notice of a floor is issued;

FIG. 7 shows an example of the structure of a packet of the floor grantsignal shown in FIG. 6;

FIG. 8 is a sequence chart showing another example of the operationsperformed when an advance-release-notice of a floor is issued;

FIG. 9 shows the process of initiating a PoC communication from thestate in which a communication channel has not been established;

FIG. 10 shows the state of a registration process;

FIG. 11 shows the state of an invitation process;

FIG. 12 shows the process of acquiring a floor in the state in which aPoC communication is performed;

FIG. 13 shows the process performed when a floor cannot be acquired inthe state in which a PoC communication is performed;

FIG. 14 shows the process of releasing a floor in the state in which aPoC communication is performed;

FIG. 15 shows the hierarchical structure of a protocol used in the PoCcommunication system;

FIG. 16 is a sequence chart showing the operation performed when a PoCcommunication is initiated; and

FIG. 17 is a sequence chart showing the operation performed when a flooris released.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The modes for embodying the present invention are described below byreferring to the attached drawings. In the description below, the commoncomponents in the figures are assigned the same reference numerals.

(Configuration of PoC Terminal)

FIG. 2 is a block diagram showing an example of the configuration of aPoC terminal according to a mode for embodying the present invention. InFIG. 2, the PoC terminal according to the present mode for embodying theinvention includes a communication unit 11 for communication with anexternal device such as a PoC server, etc., a storage unit 12 forstoring various types of information, an input unit 13 for inputtingvarious types of information, a display unit 14 for displaying varioustypes of information, and a CPU (central processing unit) 15 forcontrolling each unit.

The storage unit 12 stores, for example, a member list of membersperforming a PoC communication, a group list of groups. The group namein a PoC communication is associated with the identification informationabout a terminal which has currently acquired a floor and stored in thestorage unit 12.

The input unit 13 includes an operation button for use in performing aPoC communication.

(Configuration of PoC Server)

FIG. 3 is a showing an example of the configuration of a PoC server. InFIG. 3, the PoC server according to the present mode for embodying theinvention includes a communication unit 21 for communication with anexternal device such as a PoC terminal, etc. a storage unit 22 forstoring various types of information, an input unit 23 for inputtingvarious types of information, a display unit 24 for displaying varioustypes of information, and a CPU (central processing unit) 25 forcontrolling each unit.

(When PoC Communication is Initiated:)

FIG. 1 is a sequence chart showing the operation of the entire PoCcommunication system using a PoC terminal and a PoC server according toa mode for embodying the present invention. In FIG. 1, the operations ofthe terminal TA, the terminal TC, and the PoC server 100 are shown whenthe PoC communication is initiated.

To initiate the PoC communication, when a predetermined button ispressed in the terminal TA (S101), a SIP session establishing process isperformed between the terminal TA and the PoC server 100 (S102). The SIPsession establishing process is also performed between the PoC server100 and the terminal TC (S103).

Then, unlike the case shown in FIG. 16, the PoC server 100 sets a floorin a release state (S104 a), and transmits a floor idle signalindicating that the floor is in an idle state to the terminal TA and theterminal TC (S104 b, 104 c). Thus, the user of the terminal TA and theuser of the terminal TC can recognize that the floor is in the idlestate (S105 a, 105 b). The floor idle signal is transmitted and receivedin an APP packet.

As described above, in this system, after the establishment of a PoCsession, a calling user (user of the terminal TA) and a called user(user of the terminal TC) are notified that a floor is in an idle state.Thus, since it is controlled that the PoC communication is initiatedfrom the state in which a floor is idle, the floor can be fairlyacquired.

(Structure of Packet)

FIG. 4A shows an example of the structure of an APP packet. In FIG. 4A,the APP packet includes the number “V” indicating the version of theRTP, “P” which is a bit indicating the presence/absence of a Paddingoctet, “Subtype” defined for a unique name of an APP packet set, orapplication-dependent data, “Packet Type” for identification of a packetas an APP packet of the RTCP, “Length” indicating the length of apacket, “SSRC” as an identifier indicating the source of the RTP packet,“Reason code”, and “Additional information”. When “Subtype” is “6”, itis indicated that this packet is floor revoke in the PoC application.

As shown in FIG. 4B, “Reason code” has the following meanings. That is,“1” indicates “Only one User”, “2” indicates “Talk burst too long”, and“3” indicates “No access to floor”. In addition, “4” added in thepresent mode for embodying the invention indicates “Floor grace periodannounce”. In this case, the remaining time of the floor is set in“Additional information”. In the case of “2”, the time taken to acquirethe next floor is set.

(Floor Release-Notification)

The exemplary operation performed when an advance-release-notice of afloor in the present mode for embodying the invention is described belowby referring to FIG. 5. In FIG. 5, it is assumed that the PoC server 100transmits a floor grant signal to the terminal TA which has acquired afloor (S300). Then, the PoC server 100 transmits a floor revoke signalto the terminal TA which has acquired a floor (S301). Unlike the caseshown in FIG. 17, the floor revoke signal also means the notification ofthe remaining time of a floor. Therefore, the PoC server 100 does nottransmit a floor revoke signal immediately before releasing a floor, buttransmits a floor revoke signal only a predetermined time before therelease time.

The terminal TA which has received the floor revoke signal gives theuser a warning that a floor is to be released soon by voice, display onthe display unit, the vibration, etc (S302). The value of remaining timeof a floor can be displayed on the display unit. After the warning isgiven, the user can continue acquiring the floor within the remainingtime of the floor.

Afterwards, when the expiration time of the floor comes (the remainingtime of the floor is 0), the floor is released, and the PoC server 100transmits a floor idle signal indicating that the floor is released tothe terminal TA (S303).

Furthermore, a warning can be issued before the termination of a floor.An example of an operation in this case is explained by referring toFIG. 6. In the present embodiment, as in the case shown in FIG. 5, thePoC server 100 transmits a floor grant signal to the terminal TA thathas obtained a floor (S350). However, unlike the case shown in FIG. 5,the floor grant signal includes the information about the remaining timeT2 up to the termination of the floor and the information about thealert margin Tam indicating the time from the warning operation to thetermination of the floor.

Upon receipt of the notification, the terminal TA activates the timer,and starts counting the time of the remaining time T2 up to thetermination of the floor (S351). The timer can be realized by thesoftware in the terminal TA. When the remaining time counted by thetimer reaches the alert margin Tam, the terminal TA notifies the user byvoice, display on a display unit, vibration, etc. that the floor is tobe released soon (S352).

Otherwise, upon receipt of the notification, the terminal TA can obtainthe time up to the warning operation by subtracting the alert margin Tamfrom the remaining time T2 up to the termination of the floor, activatethe timer, and start counting the remaining time up to the warningoperation (S351). The timer can be realized by the software in theterminal TA. In this case, when the remaining time counted by the timerreaches 0, the terminal TA notifies the user by voice, display on adisplay unit, vibration, etc. that the floor is to be released soon(S352).

The value of the remaining time of a floor can also be displayed on thedisplay unit. After the warning is issued, the user can continuespeaking within the remaining time of the floor. The remaining time T2up to the termination of the floor is, for example, 30 seconds, and thealert margin Tam is, for example, 5 seconds.

Then, the PoC server 100 transmits a floor revoke signal immediatelybefore the floor is released (S353). Thus, the floor is released, andthe PoC server 100 transmits to the terminal TA a floor idle signalindicating that the floor is released (S354).

That is, in the present example, by transmitting a notification of theremaining time up to the termination of the floor and the alert marginindicating the time from the warning operation to the termination of thefloor when a floor permission notification is issued, the time up to thewarning operation is noticed for an advance-release-notice. Thus, byincluding the remaining time up to the termination of the floor and analert margin in the floor grant signal as a floor permissionnotification, the time from a warning to the termination of the floorcan be leveled independent of the model specification on the PoCterminal side, there by realizing a leveled PoC service. Furthermore,without a floor grant signal, the remaining time up to the terminationof the floor and the alert margin can be transmitted by a signal as awarning of floor termination. However, in this case, there will be morenumber of signals.

FIG. 7 shows an example of the structure of a packet of the floor grantsignal shown in FIG. 6. In FIG. 7, unlike the case shown in FIG. 4A,“Subtype” is “1”, showing that the packet is Floor Grant. Relating tothe remaining time “T2-timer” up to the termination of the floor, afterthe contents of “101” as an identifier, and “2” octet as the length ofthe information, the information “Stop talking time value” indicatingthe value of the T2 is inserted. Furthermore, relating to the alertmargin “Alert-margin”, after the contents of the identifier “xxx” (aspecific value is not fixed), and “2” octet as the length of theinformation, the information “Alert-margin value” indicating the valueof the alert margin is inserted. Relating to the “p-count” indicatingthe number of participants, after the contents of “100” as anidentifier, and “2” octet as the length of the information, theinformation about the number of participants is inserted between the“T2-timer” and “Alert-margin”. The information about the number ofparticipants can be omitted.

When the information about the remaining time of a floor (that is, theperiod up to the expiration time) is included in the floor grant signalto be transmitted when a floor is acquired, and then transmitted, it isnot necessary to transmit the floor revoke signal shown in FIG. 5. Inthis case, as shown in FIG. 8, when the notification that a floor hasbeen acquired is transmitted, the PoC server 100 transmits a floor grantsignal to the terminal TA which has acquired a floor (S400). The floorgrant signal includes the information about the remaining time of afloor, and the timer is activated in the terminal TA (S401). When apredetermined time before the expiration time of the floor is reachedbased on the time kept by the timer, the warning that the floor willsoon be released by voice, display on the display unit, the vibration,etc. (S402). The value of the remaining time of a floor can be displayedon the display unit. After the warning is given, the user can continueacquiring the floor within the remaining time of the floor.

Then, when the expiration time of a floor is reached (the remaining timeof the floor is zero), the floor is released, and the PoC server 100transmits a floor idle signal indicating the idle state of a floor tothe terminal TA (S403).

Thus, if at least one of the advance-release-notice of a floor, theremaining time of a floor, and the time taken up to an issue of awarning for an advance-release-notice is noticed by the PoC server 100,a warning that a floor will soon be released can be given to theterminal TA. That is, if the advance-release-notice of a floor isincluded in a floor revoke signal, a warning can be issued apredetermined time after the reception time. If a remaining time of afloor or the time taken up to an issue of a warning for anadvance-release-notice is included in the floor grant signal, the timeris to be activated depending on the received contents, and a warning isto be issued when a predetermined time before the expiration time of afloor is reached based on the time kept by the times.

(Floor Control Method)

In the above-mentioned PoC communication system, the following floorcontrol method is read. That is, a floor control method for controllinga floor in a PoC communication including a step (S104 a shown in FIG. 1)of setting a floor idle state in the PoC communication after a sessionestablishing process necessary for the PoC communication, and a step(S104 b, S104 c shown in FIG. 1) of notifying a PoC terminal whichperforms the PoC communication that the floor is idle is realized. Asshown in FIG. 1, when the PoC communication is initiated, a floor idlestate is simultaneously notified to both calling and called users,thereby realizing fair acquisition of a floor.

Additionally, the floor control method for controlling a floor in a PoCcommunication, and including a step (S301 shown in FIG. 5, S350 shown inFIG. 6, and S400 shown in FIG. 8) of notifying a PoC terminal which hasbeen provided with a floor of at least one of an advance-release-notice,a remaining time of the floor, and the time taken up to an issue of awarning for an advance-release-notice before releasing the floor isrealized. As shown in FIG. 5, 6, or 8, by notifying the PoC terminalwhich has acquired a floor of an advance-release-notice of the floor,the remaining time of the floor, and the time taken up to an issue of awarning for an advance-release-notice, the convenience of the user canbe enhanced.

Furthermore, the floor control method including a receiving step (S301shown in FIG. 5, and S400 shown in FIG. 8) of receiving anadvance-release-notification of a floor transmitted from a PoC serverwhich controls a floor in a PoC communication, and a warning step (S302shown in FIG. 5, and S402 shown in FIG. 8) of performing a predeterminedwarning operation when the advance-release-notification is received inthe receiving step is realized. As shown in FIGS. 5 and 8, when anadvance-release-notification is received, the notification is made byvoice, display on a display unit, vibration, etc., thereby enhancing theconvenience of a user.

CONCLUSION

In the current specification of the OMA, a connection request useracquires a floor when a called user receives a call. However, in thepresent invention, a PoC communication is controlled to be initiatedfrom the state in which a floor is idle. Therefore, a floor can befairly acquired.

Furthermore, in the current specification of the OMA, when a flooracquired for a predetermined time is released, it is a mere notice to auser. On the other hand, according to the present invention, theremaining time of a floor is noticed to a user. Therefore, theconvenience of a user can be enhanced.

The present invention can flexibly correspond with the needs of users bydifferentiating the procedure of services about the control of theacquisition of a floor in a PoC communication service.

1. A Push-to-Talk Over Cellular (PoC) server which controls a floor in aPoC communication, the server comprising: setting means for setting afloor idle state in the PoC communication to all terminals that willparticipate in the PoC communication, after a session establishingprocess necessary for the PoC communication is performed and before thesession starts; and floor release-notification means for notifying allthe terminals that will participate in the PoC communication of a signalindicating that the floor is released; wherein the PoC communicationstarts with the floor being released.
 2. A Push-to-Talk Over Cellular(PoC) server which controls a floor in a PoC communication, comprising:advance-release-notification means for notifying a PoC terminal whichhas acquired a floor for a predetermined time of at least one of anadvance-release-notice, a remaining time of the floor, and time up to awarning operation for advance-release-notice before releasing the floor;wherein when the advance-release-notification means gives a notice oftime up to a warning operation for the advance-release-notice, the meansnotifies of the remaining time up to termination of a floor and an alertmargin indicating time from the warning operation to the termination ofthe floor when a floor permission notification is issued.
 3. APush-to-Talk Over Cellular (PoC) terminal, comprising: reception meansfor receiving an advance-release-notification of a floor transmittedfrom a PoC server which controls a floor in a PoC communication; andwarning means for performing a predetermined warning operation when thereception means receives the advance-release-notification; wherein thereception means receives the remaining time up to termination of a floorand an alert margin indicating time from the warning operation to thetermination of the floor when a floor permission notification is issued.4. A floor control method for controlling a floor in a Push-to-Talk OverCellular (PoC) communication, the method comprising: a step of setting afloor idle state in the PoC communication to all terminals that willparticipate in the PoC communication, after a session establishingprocess necessary for the PoC communication is performed and before thesession starts; and a step of notifying all the terminals that willparticipate in the PoC communication of a signal indicating that thefloor is released; wherein the PoC communication starts with the floorbeing released.
 5. A floor control method for controlling a floor in aPush-to-Talk Over Cellular (PoC) communication, the method comprising: astep of notifying a PoC terminal which has been provided with a floor ofat least one of an advance-release notice, a remaining time of thefloor, and time taken up to an issue of a warning for anadvance-release-notice before releasing the floor; wherein whennotifying the time taken up to the issue of the warning for theadvance-release-notice before releasing the floor, the step of notifyingnotifies of the remaining time up to termination of a floor and an alertmargin indicating time from the warning operation to the termination ofthe floor when a floor permission notification is issued.
 6. APush-to-Talk Over Cellular (PoC) terminal control method, the methodcomprising: a receiving step of receiving anadvance-release-notification of a floor transmitted from a PoC serverwhich controls a floor in a PoC communication; and a warning step ofperforming a predetermined warning operation when theadvance-release-notification is received in the receiving step; whereinthe receiving step receives the remaining time up to termination of afloor and an alert margin indicating time from the warning operation tothe termination of the floor when a floor permission notification isissued.